Method of drilling wells



- Patented Feb. 11, 1936 2,030,777

' UNITED STATES PATENT F FICE METHOD OF ZJ EZI ZING WELLS Harold L. Woods, Monroe, La.

No Drawing. Application June 6, 1934, Serial No. 729,343 7 Claims. (Cl. 255-1) Thisinvention relates in general to improve- In the improved method of drilling according ments in drilling wells, and particularly to a methv to the present invention, it has been found that 0d adapted to prevent sealing off of the porous .the damage and injury which ordinary or treated producing strata, by the mud-bearing fluid ordidrill muds do to poroils strata may be economi- 5 narily used during drilling, A call-y avoided by the substitution of other circu- 5 It is the object of this invention to increase the lating mediums than drill mud when the bore hole flow and yield from a well by preventing porous reaches an oil, gas, or water bearing strata.- It strata containing oil, gas, or water from being has been found that greatly-improved results can penetrated and clogged by drill muds. be obtained by the use of a suitable acid solution It is another object of this invention to conas the drill fluid while drilling such strata, or in 10 stantly open up the pay strata containing oil, general by the use of a. fluid adapted to distintegas, or water while they are being drilled as disgrate the material of which such strata are comtinguished from the usual sealing action which orposed instead of sealing oil the same. dinary drill fluids produce in such porous strata. I The invention contemplates the use of any It is the further object of this invention-to drill suitable acid, such as commercial hydrochloric, 15 a bore hole which will be in a condition to pronitric or sulphuric acid, or mixtures thereof, for duce oil, gas, or water as the case may be imexample, in drilling operations where the producmediately at the conclusion of the drilling operaing stratum consists of 'lime or calcareous formation and without any necessity for cleaning or distion. The acid or acids used may be of any suitsolving colloidal drill mud out of the pores of theable concentration and may have an inhibiting 20 producing strata. l agent, such as 1 to 10% of a soluble arsenic com- With the present methods of drilling wells by pound, mixed therewith to minimize corrosive acthe use of a rotary cutter, it is customary to pump tion on the well casing, drill stem, and like appaa drill mud downward, through the drill stem ratus with which the drill fluid comes in contact.

while drilling. The drill mud picks up the earth' The practice of this invention will now be de- 5 cuttings and conveys them to the surface as, it scribed in connection with a specific example of circulates upwardly between the drill stem and drilling. In the Many-Zwolle field in Sabine the bore hole casing. Parish, Louisiana, a well is drilled to a depth of Ordinary drill mud consists offlnely divided twenty-three hundred feet by the use of ordiclays and similar matter suspended in a liquid to nary drill mud and drilling apparatus. At this 30 form a slush of the'desired viscosity. The drill level the top of a lime, chalk, or marl formation mud at the lower end of the bore hole being drilled is reached. A casing is set and cemented and is'under considerable pressure due to the weight the ordinary drill mud is removed from the well. of the column of fluid above. This pressure nor- The rotary drill stem is returned to the bore hole mally causes the drill mud 'to penetrate laterally which is then fllled with a suitable inhibited acid 35 into the porous strata encountered in drilling and solution, for example, a 23-25% hydrochloric acid to seal off these strataby closingor clogging the solution. As the drilling then progresses through pores existing therein. the porous pay formation, the acid circulating The producing strata are generally of a porous fluid acts immediately on this stratum and in- 40 nature and suffer considerable damage when creases the size of the pores and the cavities 40 drilled with. conventional drill mud. It is both therein. Asthere is no drill mud present at'this diflicult and expensive to remove the drill mud level, the porous formation never is penetrated from the porous pay strata once it has'penetr'ated or clogged by colloidal muds but is constantly into the same. To avoid this damage, it has been cleaned and opened by the action of the acid cir-' heretofore proposed to treat the drill muds chemculating fluid. After the drilling operation is as ically to lessen their degree of penetration into completed, the well is immediately ready for proporous strata. It has also been proposed to treat ducing;

the bore hole with chemicals after it has been As the acid drill fluid is used only while drilling drilled in order to clean out as far as possible the porous pay strata, the acid is used where it this connection, acids have been used to clean out fit and it is not lost or consumed by leakage into the colloidal drill muds which have penetrated non-pay formations. If the acid were used for a into and clogged up thfi porous formations during circulating fluid during the drilling of the endrilling andto enlarge' the cavities in such ionnatire well, the losses would be so great that the 55 tions. coat of the acid would be prohibitive. Where the drill mud which has clogged the pay strata. In can produce the greatest possible amount of bene- 50 I bore is treated with acids after drilling, the acids are often lost through the most porous part of the strata, the other sections of the porous strata remaining untreated. Also the subsequent treatment with acid after the stratum has been scaled 01!, does not produce results comparable with these obtained by the process described. Confining the use of the acid to the drilling of the porous pay strata enables the acid to be used most effectively andeconomically.

Although it is preferred to circulate the acid solution downwardly in the" drill stem and upwardly between the stem and easing as in the case of conventional drilling-it is also possible to achieve the desirable results of this invention byallowing the acids merely to stand in the bore hole during a part or the entire period that the porous pay strata is being drilled.

From the above description it will be apparent that by the use of this improved method of drilling through porous strata in the presence of acids, the bore hole will be in its best possible producing condition when drilling has reached the desired level; that it will be unnecessary to undertake subsequent cleaning operations to remove muds from the porous strata; and that much better results are possible than those obtained merely by subsequent attempts to clean the'pay strata after the drilling has been completed.

I claim:

1. In ,well drilling operations, the method of opening the pores of porous producing formations, which comprises removing the mud circulating fluidsupon reaching said formation, introducing an acid solution into the well and'con'ducting the drilling operation in the producing formationjin the presence of saidacid solution.

2. Inwell'drilling operations, the method com prising drilling the initial portion of the well in the presence of a'mud circulating fluid, removing the mud circulating fluid, substituting an acid and continuing with the drilling in said stratum 20 solution therefor, and then drilling that portion of the well which traverses porous producing strata while circulating therein the said acid solution.

3. In well drilling operations, the method of protecting porous producing strata from being damaged by drill muds, which comprises drilling the initial non-porous portion of the well in the presence of a mud fluid, then removing the-mud fluid from the well, introducing an-acid intothe w well, and drilling said porous strata in the pres- 5 ence of said acid. p

4; In well drilling operations, the method comprising initially drilling in the well while circulating mud fluid through the boring until a pro.- ducing stratum is reached, then'removing said mud fluid and introducing into the well a fluid having the chemical property of disintegrating the material of which said stratum is composed, I

in the presence of the said disintegrating fluid. '.5. In well drilling operations, the method comprising circulating mud fluid through the boring during the initial drilling and until a calcerous producing stratum is reached then: replacing the the drilling while circulating the hydrochloric acid through the boring.

6. In well drilling operations, the method comprising drilling the initial part of the well and 30 to a depth which extends through the non-producing' strata in the presence of a mud circulating fluid, then removing said mud fluid from the boring, substituting therefor an acid solution containing hydrochloric acid of from 5 to 25% con- 30 .centration together with a corrosion inhibitor of CERTIFICATE oi cosss'crioii.

eatentwolaosonv'r;

mud fluid withtliydrochloric acid and continuing February 11; 1931 HAROLD: 'woons;

It is hereby certified that error, appears in the printed specification of the above numbered patent requiring cbrrection as follows: Page l,- second column, line 11-12, for distintegrate'! read disintegrate; same page and column, line 14, for "The" read This;' page 2, second column, lines 24 and 58 claims Sand 6 respectively, for "calcerous" read calcareous; and that the said Letters. Patent should be read with these corrections therein that the same mayoonform to the record of the case in the Patent Office.

Signed and sealed this 3rd day of March, A. D. 1936.

Leslie Frazer (Sea-1) Acting Commissioner of Patents.

CERTIFICATE or common.

Patenvno; 2,050,777; February 11; 19a

' mono L 'woons;

It is hereby certified that error appears in the printed specification of the above'numbered patent requirihg-chrrection as follows: Page l,- second column, line 11-12,- for "distinteg rate'! read disintegrate; same page and column, line 14, for "The" read This;' page 2, second colpmn, lines 24 and 38 claims- 5imd 6 respectively, for "calcerous" read calcareous; and that the said Letters. Patent Js'hqulgi be read with these corrections therein that the same majr conform to the record-of the case in the Patent Office.

Signed and; sealed thisSrd day of March, A. D. 19:56.

v Leslie Frazer (Seal) Acting Commissioner 01f Patents. 

